Method for distilling hydrocarbon oils



METHOD FOR DISTILLING HYDROCARBON OILS File May 28, 1930 s Sheets-Sheet1 INVENTOR y 16, 1933- s. c. YEATON 1,909,600

METHOD FOR DISTILLING HYDROCARBON OILS Filed May 2 1930 5 Sheets-Sheet 2INVENTOR y 16, 1933- s. c. YEATON 1,909,600

METHOD FOR DISTILLING HYDROCARBON OILS Filed May 28, 1930 5 Sheets-Sheet3 23 24 1T1; J36 W 57 INVENTOR May 16, 1933. s. c. YEATON 1,909,600

METHOD FOR DISTILLING HYDROCARBON OILS Filed May 1930 5 Sheets-Sheet 4INVENTOR May 16, 1933. s. c. YEATON 1,909,600

METHOD FOR DISTILLING HYDROCARBON OILS File May 1930 5 Sheets-Sheet 5FIG-.5:

Patented May 16, 1933 PTATET OFFICE SAMUEL G. YEA'ION, OF BAYSIDE, NEWYORK METHOD FOR DISTILLING HYDROCARIBON OILS Application filed May 28,

This invention relates to improvements in means and methods fordistilling hydrocarbon oils, and more particularly for refining suchoils involving What is commonly termed the cracking thereof.

In distilling hydrocarbon oils by a cracking process, a considerableamount of carbon is developed, depending more or less upon the nature ofthe stock treated, Which, if not taken care of, gives much trouble andmaterially curtails the run in such modern methods as are commonlytermed continuous, all of Which is Well known in the gasolene and alliedmanufacturing industries. It has been discovered that by releasing,during the run, a portion of the oil charge from the still containingthis objectionable carbon, the length of the run may be materiallyincreased. It is to such apparatus and methods of manufacture ofgasolene and the like involving a relieving of the charge of a part ofits carbon-contained oil during the cracking process that the presentinvention is directed.

A common type of such set-up for carrying out the method includes aheating element Where the charge of oil is heated to a crackingtemperature; means for relieving the element of carbon-contained oil; areceiver for receiving a portion of theoil discharged from the chargeWithin the element after a cracking treatment; means for supplying oilto the charge Within the element from the receiver; and means forfeeding fresh oil to the charge. In set-ups of this type it has been thecommon practice to relieve the charge of the desired portion ofcarbon-contained oil While oil is being supplied to the charge from thereceiver, in a manner to permit this supply to commingle with theportion of the charge therein that is being released.

The principal object of this invention is to provide for an intermittentreleasing of r a porton of the carbon-contained oil from the charge, andto provide means, during this period, to prevent such commingling of theoil supplied to the charge fi'om the receiver.

This improvement is particularly advanthe carbon-contained oil.

1930. Serial No. 456,361.

tageous in such methods and types of apparatus provide for dischargingthe oil from the charge to the receiver in vapor form, after Which aportion of the discharge is condensed in the receiver and supplied inliquid form therefrom to the charge. This vapor discharge from theelement has, previous to its discharge, as is obvious, been submitted toa cracking temperature in the heating element, and therefore presents amuch purer stock than the carbon-contained charge in the element. As itis only necessary, in clearing the system, to remove the heavycarbon-contained oil, it can be readily seen that this relatively puredischarged stock should not be supplied to the element to commingle Withthe heavier stock therein that is being carried out of the system by therelieving means. In short, this relatively pure discharged stock issupplied to the charge in the heating element for the sole purpose ofbeing recracked and thereafter to again be discharged to the receiver.Therefore it is obvious that to prevent this commingling of therelatively pure oil With the carbon-contained stock that is beingreleased, efi'ects an economy in the method of manufacture.

While the invention contemplates broadly the prevention of thisundesirable commingling, in the preferred embodiment the supply from thereceiver to the element takes place intermittently, the supplying ofsuch oil being alternately With the releasing of It has beenfoundadvantageous for several Well-known reasons to maintain a substantiallyconstant charge in the heating element, and as such intermittency offeed would temporarily interrupt this constancy, the invention furthercontemplates, if desired, feeding a fresh stock to the charge in theheating element during the releasing period, to maintain the chargesubstantially constant. The fresh stock may be permitted to commingle ornot, with the portion being released for it Will not be particularly diadvantageous to so handle it especially Where the fresh stock representscrude oil that has not been previously subjected to a cracking ordistilling treatment. The pres ent invention further contemplates eitherpermitting or preventing the commingling of the fresh stock with thestock being released as may be desired.

A further object of the invention is to provide a new type of receiverfor receiving the discharged oil from the charge in the heating elementin vapor form, the receiver serving as a condenser for a portion of thedischarge by indirect heat transfer between the discharge in thereceiver and the fresh charge of oil to be supplied to the element. Thereceiver preferably but not necessarily comprises means for directlyfeeding fresh oil thereto. The two feeding means are supplied withvalves whereby they may operate intermittently, conjointly oralternately as desired in a manner as will more fully be hereafterdescribed.

While the heating element may be of any well-known or preferred type,the invention further contemplates, when desired, a heating elementwherein the charge of oil is heated to the required temperature bysubjecting it to the action of a heated fluid brought into indirect heatexchange relation with the charge.

Other objects of the invention will appear from the followingdescription.

In the accompanying drawings: Figure 1 is a side elevation of anapparatus involving the present invention shown diagrammatically; Fig.2, a view similar to Fig. 1, show: ing a feed for the heating elementpassing through the receiver in indirect heat exchange relation; Fig. 3,a view similar to Fig. 1, showing a valve or gate for separating thecharge in the heating element; Fig. 4, a view, similar to Fig. 2,showing the charge separating valve or gate of Fig. 3; Fig. 5, a sideelevation partly in section of a portion of the apparatus showing aheating element where the charge of oil to be heated is brought intoindirect heat exchange relation with a heated fluid; and, Fig. 6, atransverse section, taken on the line 66 of Fig. 5.

Referring to Figs. 1 to 4 inclusive, the heating element indicatedgenerally by the reference A, while it may be of any suitable type, isshown as of a type resembling the Babcock 8a Wilcox boiler comprising ahorizontal longitudinal drum 10, front trans verse drum 11, reartransverse drum 12, connecting tubes 13, front sluice way 14, rearsluice way 15, a fire box 16, oil burner 17, safety valves 18, andpropeller and electric motor for driving same, generally indicated bythe numeral 19, same being employed in a usual way for increasing thetravel of the oil charge through the still in the direction indicated bythe arrows.

While the invention is not confined to any r u o q n part1cular meansfor rel1eving the charge 1n the heating element of a portion of thecarbon-contained oil, in the present instance, except for the employmentof a control valve, a well-known means is shown which romprisesvaporizer 20, pipe 21, leading from the heating element to theevaporator through which the carbon-contained oil release is carried,said pipe being shown in Figs. 1 and 2 as leading from the fronttransverse drum 11, control valve 22, to 3rovide for intermittentrelease of the carboncontained oil from the heater to the evaporator,pressure reducing valve 22, safety valve 23, vapor take-oil pipe 24, andresiduum take-off pipe 25, leading from the evaporator.

The receiver, indicated generally by the reference B, for receiving thedischarge from the charge of oil may be of any suitable type of refluxtower or dephlegmator, modified as will appear presently. In the presentin stance, it comprises vertical drum 26, pro vided with horizontalbaffles 27, vapor takeoff pipe 28, and safety valve 29. The discharge ofoil vapor is conveyed through a pipe 30, leading from the drum 10, tothe receiver drum 26, and oil is supplied through a pipe 31, leadingfrom the receiver to the heating element, which pipe, in Figs. 1, 2 and4, is provided with a control valve 32, for intermittently supplyingsuch oil to the charge in the heating element alternately with therelease of the carbon-contained oil through the pipe 21, as willhereafter more fully appear. The receiver, or reflux tower is providedwith a coil trim, 33, to which a cooling fluid is lead through the pipe34, the fluid after passing through the trim being discharged throughpipe 35, in the usual manner.

Fresh oil is fed to the receiver through pipe 36, provided with controlvalve 37. Fresh oil is fed to the heating element, which in the presentinstance, as shown in Fig. 1, is accomplished by feeding it through apipe 38, provided with a control valve 39, said pipe 38, forconvenience, leading from pipe 36 to pipe 31 below the valve 32. Thetake-off pipe 40 provided with control valve 41 leads from pipe 31 abovevalve 32.

In Fig. 2 the feed pipe for feeding fresh oil to the receiver isprovided with a control valve 42, near the upper end thereof, and thefeeding of fresh oil directly to the heating element is accomplishedthrough a pipe 43, provided with a control valve 44, lead ing to theheating element and connected at its upper end to a heat exchangerelement disposed in the receiver and indicated diagrammatically by thewinding pipe 45, passing back'and forth between the bailies 27. Thisheat exchanger is connected at its upper end to a pipe 46, leading frompipe 36, below the valve 42.

Fig. 3 shows a form of apparatus somewhat similar to Fig. 1, except nodirect feed of fresh oil is provided for the heating element, and notake-off pipe from the receiver is employed. In this form of apparatus,the drum 10, is divided in two parts at a suitable point in the lengththereof, as actual practice willdictate, with a separating valve orgate, which is shown in the present instance as a butter-fly type ofvalve 47, mounted on a horizontal transverse shaft which extends throughthe drum. The shaft is provided with a handle, 48, for opening andclosing the valve, flanges 4L9, being provided on the inner walls of thedrum for seating the valve when in closed position. The normal level ofoil charge in the drum is shown by the line w,.which may be at anysuitable height. The valve may divide the drum transversely throughoutits entire height in which case a second discharge pipe similar to pipe30 would be required at the opposite end of the drum leading to thereceiver at substantially the same point as does the discharge pipe 80.In the form shown, however, the valve 47 is shown as not entirelydividing the upper or vapor space of the drum 10. Therefore, the vaporspace on both sides of the valve when closed being in communication, asingle discharge pipe 30 is all that is necessary. In this form ofapparatus the release pipe 21 leads from the drum 10 at a pointconveniently near the surface of the oil charge therein, butsufiiciently below such surface to be still covered by the oil charge atthe termination of the release period, it being desired in this form ofapparatus to release the carbon-contained oil from the charge during there leasing period without removing any appreciable amount of the newlysupplied oil that might circulate from the supply end of the drum to therelease end through the bank of tubes 13. To further safeguard againstthis the supply from pipe 81, in this form of apparatus preferablyenters the heating element at or above the surface of the charge of oil.

Fig. 4c shows a form of apparatus similar to that of Fig. 3 with theexception that the direct feed to the heating element and the take-offpipe from the receiver, shown in Fig. 2, are provided.

l/Vhile the heating element has been thus described as of the Babcock &Wilcox type of boiler, a. modified type of heating element is shown inFigs. 5 and 6. This type of heating element is patterned after the steamboiler shown in United States patent to Hartmann, No. 1,663,910, andreference may be there had for a more complete understanding of such atype of boiler. In the present instance, it comprises briefly, ahorizontal drum 50, provided with an oil feed pipe 51, a discharge pipe52, and a release pipe 53, for the carbon-contained oil. The

heat is supplied to the drum 50 by the indi rect fluid-containedheat-exchanger, indicated generally by the reference C, and as showncomprising a fire box, D, receptacles, E, E extending longitudinally ateach side of the fire box, and longitudinally extending drums F, Fdisposed above the receptacles E, E. Each receptacle is connected to adrum above it by a series of tubes 54:, and to a drum on the oppositeside by a series of tubes 54. The large. drum 50 is separated fromdirect contact with the heat of the fire box by the separating walls 55.

Two series of heat exchanger units are shown. Each unit of one seriescomprises a bank of tubes 56, disposed in the drum 50 each tube beingbent back and forth upon itself and connected at its ends to headers asshown. The upper header of each unit is connected to a pipe 57, leadingto the drum F, and the lower header is connected to a pipe 58 leading tothe receptacle E, passing thereto on the outside of theheater. The otherseries of units is likewise disposed in the drum 50. Each unit comprisesasimilar bank of bent tubes 56, having its upper header connected to apipe 57 leading to the drum F and its lower header connected to a pipe58 leading to the receptacle E passing thereto on the outside of theboiler.

These heat exchange units, as is obvious, form, taken collectively, aclosed system for fluid which may be water, oil, or other heattransferring medium that can be heated to the required temperature, andsuch medium should be of a purity, as for instance distilled water, pureoil, etc., that may be continuously used in the closed system withoutproducing any appreciable precipitate or incrustations on the conveyingtubes of the system, all in the usual manner in such apparatus. While nofeed is shown for this exchanger, a relatively small feed may benecessary to take care of leakages etc., as more fully set forth in theabove mentioned Hartmann Patent No. 1,663,910.

A number of power driven rotatable cylindrical brushes indicated at Gmay, when desired, be employed in the drum 50, similar to those shown inthe patent to Smith No. 1,324,07 5, for producing a circulation of oilthrough the drum.

This type of heater as shown is appropriate for use in the forms of setup shown in Figs. 1 and 2 but it is obvious that it may i be modified toinclude the valve 47 of Figs. 3 and 4 and be made to operate similarlythereto.

In continuous cracking stills in common use where carbon is producedduring cracking of the oil, even in the most favorable circumstances,and with the best precautionary measures, carbon will, to some extent,precipitate and form a crust on the metal surfaces, and the system Will,in time, be-

come sufficiently clogged with the carbon and other residuums to requireshutting down and complete cleaning out. The incrustations are foundlargely on the tubes that come in direct contact with the heat of thefurnace, such for instance as the tubes 13 of the Babcock & Wilcox typeof boiler shown in Figs. 1 to 1. In Figs. 5 and 6, all such trouble isavoided by the indirect fluid heat exchanger employed.

The operation of the apparatus, refer ing first more particularly toFig. 1, is as follows:

When the still is under normal cracking operation the valves 22, 39 and41 are closed, all other valves being open, the propeller 19 beingdriven in the usual way to increase the circulation of the charge in thestill, as indicated by the arrows. During this period of operation freshoil is fed through the pipe 36 to the receiver drum 26, and a supply ofoil is fed from the receiver drum 26 through pipe 31 to the heatingelement, A. The oil fed through pipe 36 may come from any desiredsource, as the usual make up tank, and may be of any desired grade,crude petroleum, pretreated stock, etc., and may contain otheringredients as is usual in make up stock.

The pipe 36 entersthe receiver at a point near the top from where theoil descends in a zig-zag path through the system of bailies 27, forminga direct heat exchanger for the vapors of the discharge from the heatingelement A, which enter the receiver, from the pipe 30, near the bottomthereof, and ascend therethrough. Part of this discharge is thuscondensed and passes, with the fresh feed or" liquid, through the pipe31 to the heating element. The part of the discharge in the receiveruncondensed passes out through the pipe 28 as vapor in the usual manner.

When it is desired to relieve the charge of part of the carbon-containedoil, the valves 22, 39 and 4-1 are opened, and the valve 32 closed. Thispermits the desired carboncontained oil to be released from the heatingelement, A (due to the pressure of the charge); a take-off of the oilfrom the receiver through the pipe 40; and a feeding of the fresh oil tothe heatingelernent A through the pipe 38. When suiiicientcarbon-contained oil has been released, the valves are then set in theirnormal cracking positions as first described. The releasedcarbon-contained liquid, in the present embodiment, passes through areducing vaive, 22', and enters the vaporizer 20, where it is partiallyvaporized, the vapor passing off through the pipe 24, the residuumPESSQS off through the pipe 25 in a well known manner.

It will be noted that during the reiief period, the fresh oil is beingfed to the receiver through the pipe 36, and, with the condensateportion of the discharge, is taken off through the pipe 40, thereby inno way interrupting the action of the dephlegmator or reflux tower, B,during this relief period when the contents of the receiver B is shutoff from the heating element by the closing of the valve 32. Likewisethe valve 39 being open, fresh oil is fed, during this period of relief,to the heating element, thereby making it possible to maintain aconstant volume of charge therein.

The operation of the apparatus of Fig. 2 varies slightly from that ofF 1. When the still is under normal cracking operation the valves 22, i1and i i are closed. The apparatus then operates in a manner similar tothat of Fig. 1, during this period. Then it is desired to relieve thecharge of carboncontained oil, the valves 22, 1-1 and are opened and thevalves 32 and [L2 closed. This permits the feed of fresh oil to theheating element during this period of release to pass through thereceiver in indirect heat exchange relation with the discharge therein,thereby avoiding the necessity during this period of feeding fresh oildirectly to the receiver through the pipe 36. This receiver thusoperates, during this period, as a de phlegmator or reflux tower withoutthe necessity of passing a direct feed th. :ethrough, and then taking itoff with the discharge through the pipe 40, which would be in someinstances a useless operation and wasteful of heat. While in Fig. 2, adirect feed through the pipe 36 to the receiver is shown, this may beomitted, and the feed to the heating element through the heat exchanger45 solely relied upon as a feed to the heating element, and a heatexchanger for the condensation of the vapors to be condensed in thereflux tower, in which case the valve 44 would be continuously open. Andas another alternative, where the direct feed to the receiver throughpipe 36 is employed, both this feed and the feed through the pipe 43 maybe employed during the normal cracking operation, the respective valvesgoverning these feeds being suitably adjusted to provide for the properamount of feed. In this case, the feed from the pipe 43 to the heatingelement will be continuous, but regulated to maintain a substantialconstancy of the charge during the release period when the feed froa.the re ceiver to the heating element is discontinned.

When the still of the form shown in Fig. 3 is in normal crackingoperation, the valve 22 is closed, and the valve or 47 open. During thisperiod, the apparatus operates in a manner similar to other well knowntypes of apparatus, except that no release of carbon-contained oil isbeing effected during this period. Fresh .oil is continuously fed to thereceiver and the supply therefrom to the heating element is likewisecontinuous. When it is desired to relieve the charge of carbon-containedoil, the valve 22 is open and the valve, 47, closed. Also during thisperiod, the propeller 19 may be slowed down or stopped entirely, asdesired, relying upon the thermal circulation in the boiler. During thisperiod of relief it will be observed that the liquid charge in the drum10, is divided by the dividing wall formed by the closed valve 47, butthat theupper vapor portions at each end of the drum are incommunication over the top of this valve, so that a free discharge ofvapor may be effected from the entire vapor contained portion of thedrum through the pipe 30. If, however, the valve 47 be made to entirelyseparate the two ends of the drum 10, so that while the valve 47 isclosed, two steam spaces are provided, a duplicate pipe similar to thepipe 30 should be led from the opposite end of the drum 10 to thereceiver. During this re lease period there is no opportunity for thecharge of oil to circulate through the drum 10 on account of the closedposition of the valve 47. Therefore the supply of oil from the receiverto the rear end of the drum 10 and the release of carbon-contained oilfrom the front end of the drum 10 should be relatively apportioned topermit a suflicient circulation of the liquid through the tubes 13 toprevent overheating of the .oil therein. In his form of apparatus, therelease pipe 21 extends below the surface of the oil in the drum 10, andthis should be to a suflicient extent only, to permit the desired amountof carbon-contained oil to be removed, which removal should preferablybe at or near the surface of the charge of oil in order that therelatively pure oil being fed to the drum 10, (which by thermalcirculation will travel over to the forward end of the drum via thetubes 13) will not have reached the release pipe 21 until the desiredamount of carbon-contained oil has been released and the valve 22closed.

Fig. 4 shows a form of apparatus involving the valve 47 and rellef pipe21 similar to that shown in Fig. 3, but otherwise the construction issimilar to that shown in Fig. 2 and the operation is similar to thatdescribed in connection with Fig. 2 except that when the release ofcarbon-contained oil is taking place, the valve 47 is closed, as in Fig.3. The feed of fresh oil through pipe 43 during this period is preventedfrom commingling with the carbon-contained oil being released in likemanner as the supply from the receiver to the heating element wasprevented from commingling in the form shown in Fig. 3.

It will be apparent from the foregoing that the instant inventionprovides a new and improved process which comprises the following steps:heating a charge of hydrocarbons to cracking temperatures; separatingthe vapors produced thereby from the unvaporized hydrocarbons;subjecting the unvaporized hydrocarbons to further heating to crackingtemperatures; passing the vapors in heat exchange with hydrocarbonsintroduced into the charge (the cracking system) for further charging;partially condensing the vapors in the heat exchange operation to form areflux condensate; delivering the reflux condensate for re-cracking;removing the uncondensed vapors from the charge as the product of theprocess; and the novel steps which include intermittently removingunvaporized carbon-containing hydrocarbons from the charge (or system),while at the same time diverting the reflux condensate while thecarbon-containin hydrocarbons are being withdrawn and c arginghydrocarbons are being introduced.

It will also be apparent that the aforedescribed process may be varied.In one instance, vapors may be passed in direct heat exchange with thehydrocarbons being introduced for charging, and the reflux condensateresulting from the partial condensation of these vapors may be mixedwith the charging hydrocarbons and the mixture delivered to be cracked.Here the mixture isdiverted from the charge (the cracking system) whlleunvaporlzed carbon-containing hydrocarbons are being discharged from theof the several instances will be apparent from the foregoingdescription, or will be apparent to those skilled in the art, and itwill be understood that all and any such changes and modifications asfall within the scope of the appended claims are contemplated as a partof the present invention.

While the invention is primarily directed to the manufacture of gasoleneand the like, it is not so limited, but may be used in the cracking ofhydro-carbon oils generally for the production of any product obtainabletherefrom, and while the term fresh oil and the like has been usedthroughout the description it will be understood that this is intendedto include any make-up oil whether crude petroleum or any productobtained therefrom, or combinations thereof,

and any other ingredients that may be mixed therewith, all of which iswell known.

From the foregoing it will be seen that during both the normal crackingperiod and the relieving period, provision is made for maintaining thecharge of oil in the heating element substantially constant. Thisobviously is desirable in order to maintain a uniform discharge from theheating element to the receiver and uniform maximum utilization of theheat from the furnace. Ordinarily there is considerable apparatus in acomplete set-up, beyond that shown in the drawings, which involvevarious heat exchangers, and therefore to maintain normal operation ofthese, it is important that the discharge to the receiver be uniform inorder that the vapor take-off going to certain heat exchangers from thetake-off pipe, 28, may be maintained constant. Also in set-ups where thefresh oil entering the feed pipe 36, has previously passed through heatexchangers, it may be desirable that the flow through this pipe bemaintained constant, and provision is made in the present invention toaccomplish this if and when desired, as has been described. Furthermore,the periodic take-off of heated oil from the receiver through the pipe40, may be conveyed through heat exchangers for utilizing the heatthereof, and oil therefrom passed to a tank for future use as make-upstock, or for such other use as desired. The invention contemplates thecontinued use of the reflux tower 26, as such, and the heat exchanger4-5, disposed therein performs the triple office of serving as a feed offresh oil for the charge in the heating element, of being preheated inits passage through the receiver or reflux tower 26, and of serving as acondenser for the vapors to be condensed in the receiver. It will befurther understood that the intermittent periods of normal cracking andor relief may be timed as to duration to maintain a continuous carryingon of the method, and a suitable removal of the required quantity ofcarbon-contained liquid to insure a suflicient length of run before shutdown and cleaning is necessary to render the method commerciallyprofitable. In this regard the size of the various pipes leading to andfrom the heating element will be apportioned to feed and removerespectively the desired quantities of material during the periodsalloted therefor, and of course the release will begin before too greatan amount of carbon has been liberated in the heating element. Forinstance, in the forms of apparatus shown in Figs. 3 and 4, it may befound desirable to decrease the period of relief and increase the rateof relief in order to minimize the likelihood of the fresh stockreaching the relief pipe 21 during this relief period. In methods incommon use, it has been found advantageous to maintain frequentinspection of the apparatus and therefore hand operated control valveshave been comonly used where the attendants are always on duty toregulate them in accord ance with a predetermined schedule, theattendants thus being able to maintain a careful watch as to the way theapparatus is functioning, and the method of procedure. Therefore in thepresent invention, hand controlled valves have been shown, but it isobvious that these may be replaced by power controlled valves operatedfrom a central station if desired or by timed automatic valves, whichare employed to some extent in modern apparatus.

The invention claimed and desired to be secured by Letters Patent is:

1. In a process for cracking hydrocarbon oil, wherein the hydrocarbonsare heated to cracking temperatures, vapors produced thereby areseparated from the unvaporized hydrocarbons, the unvaporizedhydrocarbons are subjected to further heating to cracking temperatures,the vapors are passed in heat exchange with charging oil for the system,a part of the vapors being condensed thereby to form a refluxcondensate, the reflux condensate is returned for re-cracking, and theuncondensed vapors are removed as the product of the process, theimprovement which comprises intermittently removing unvaporizedcarbon-containing hydrocarbons from the system while diverting thereflux condensate from the system during said removal of thecarbon-containing hydrocarbons, and continuously supplying charging oilto the system.

2. In a process for cracking hydrocarbon oil, wherein the hydrocarbonsare heated to cracking temperatures, vapors produced thereby areseparated from unvaporized hydrocarbons, the unvaporized hydrocarbonsare subjected to further heating to cracking temperatures, the vaporsare passed in indirect heat exchange with charging oil for the system, apart of the vapors being condensed thereby to form a reflux condensate,the reflux condensate is returned for recracking, and the uncondensedvapors are removed as the product of the process, the improvement whichcomprises intermittently removing unvaporized carbon-containinghydrocarbons from the system and diverting the reflux condensate fromthe system while directly supplying the system with saidindirect-heat-exchanging charging oil during said removal of theunvaporized carbon-containing hydrocarbons.

3. In a process for cracking hydrocarbon oil, wherein the hydrocarbonsare heated to cracking temperatures, vapors produced thereby areseparated from the unvaporized hydrocarbons, the unvaporizedhydrocarbons are subjected to further heating to cracking temperatures,the vapors are normally passed in direct heat exchange with charging oilfor the system, a part of the vapors being condensed thereby to form areflux condensate, the heat exchange mixture of condensate and chargingoil is delivered for cracking, and the uncondensed vapors are removed asthe product of the process, the improvement which comprisesintermittently removing unvaporized carbon-containing hydrocarbons fromthe system While diverting said mixture from the system, and during saidWithdrawal successively passing charging oil in indirect heat exchangewith said vapors and directly supplying the system with said lastmentioned charging oil.

4:. In a process for cracking hydrocarbon oil, wherein the hydrocarbonsare heated to cracking temperatures, vapors produced thereby areseparated from the unvaporized hydrocarbons, the unvaporizedhydrocarbons are subjected to further heating to cracking temperatures,the vapors are passed in heat exchange with charging oil for the system,a part of the vapors being condensed thereby to form a refluxcondensate, the reflux condensate is normally mixed With charging oilpassed in direct heat exchange therewith and the mixture delivered forcracking, and the uncondensed vapors are removed as the product 01"- theprocess, the improvement which comprises intermittently Withdrawingunvaporized carbon-containing hydrocarbons from the system anddiscontinuing direct heat exchange of the charging oil and vapors, anddiverting the reflux condensate from the system during said withdrawalWhile successively passing charging oil in indirect heat exchange Withsaid vapors and directly supplying the system With said last-mentionedoil.

5. In a process for cracking hydrocarbon oil, wherein a charge of thehydrocarbon oil is heated to cracking temperatures, vapors producedthereby are separated from unvaporized hydrocarbons of the charge, theunvaporized hydrocarbons are subjected to further heating to crackingtemperatures, the vapors are passed in heat exchange with charging oilfor the charge, a part of the vapors being condensed thereby to form areflux condensate, the reflux condensate is returned to the charge forre-cracking, and the uncondensed vapors are removed as the product or"the process, the improvement which comprises intermittently removingunvaporized carbon-containing hydrocarbons directly from the charge,While diverting the reflux condensate from the charge during saidremoval of the carbon-containing hydrocarbons, and during said divertingadding oil to the charge.

SAMUEL C. YEATON.

